Yes, New Cross carries a real flood risk, and it shows up far more on the official maps than in anyone's memory. About a third of its postcodes lie in the highest river-and-sea flood zone. Around a fifth rate high on at least one flood measure. More than half fall inside the zone drawn for a warmer climate. Nothing on record says it has flooded, though the maps are drawn for the day it does.
The Environment Agency's river-and-sea mapping puts about 36% of New Cross postcodes in flood zone 3, the band with the highest modelled chance of flooding. Another 5% lie in flood zone 2, the medium-probability fringe beyond it, which is why the second number is the smaller one. For an area that grew up as a coaching stop on the road to Dover, a surprising amount of it is drawn on the river's side of the line.
Surface water, the rain that has nowhere to go on hard-paved streets, has no zone of its own on those maps. Here it is folded into a postcode-by-postcode rating set out further down.
The agency also draws the zone as it would look under a changed climate, and about 58% of New Cross postcodes fall inside that version. It is a modelled outline of where the zone would reach as the climate shifts, and puts no date on any flood.
A flood-zone postcode follows a house into the insurance application, and cover in the top zone can cost more or come with a larger excess. The useful check is the exact address in the Environment Agency's long-term flood-risk service, followed by an indicative quote from an insurer, because the zone is drawn across postcodes and some homes inside them sit higher than others.
A wider measure asks whether each postcode rates high on at least one of several flood indicators, surface water included alongside rivers and sea. On that basis about 19% of New Cross postcodes rate high on at least one measure, about 31% medium and about 54% low. It counts a postcode once, whichever measure put it there, so it reads differently from the zone figures and the two should not be added together.
The agency's modelled flood extents put a fraction of 1% of postcodes inside the high-probability extent with no defences in the model, and none inside it with defences in place; about 4% fall inside the low-probability extent with no defences. "Defended" in that modelling means a defence is present, and says nothing about whether a particular house stays dry. One agency draws a third of New Cross in the top zone and then finds almost nothing inside its own high-probability extent, and the gap between those two maps is where insurers do their work.
The nearest tide gauge in the record is at Portsmouth, which measured sea level rising by about 2 millimetres a year between 1962 and 2023. Portsmouth is a long way from New Cross by any road, so the figure describes the sea in general and the tidal Thames only loosely.
The Environment Agency's records show no historic flooding across New Cross. That is good news, and it only covers floods somebody wrote down.
Flood risk is where New Cross comes off worst, because the official zone covers so much of it that a buyer has to take the map seriously even on streets that have stayed dry.